Question: Solve for $x$ and $y$ using substitution. ${2x+3y = -11}$ ${y = -6x-9}$
Answer: Since $y$ has already been solved for, substitute $-6x-9$ for $y$ in the first equation. ${2x + 3}{(-6x-9)}{= -11}$ Simplify and solve for $x$ $2x-18x - 27 = -11$ $-16x-27 = -11$ $-16x-27{+27} = -11{+27}$ $-16x = 16$ $\dfrac{-16x}{{-16}} = \dfrac{16}{{-16}}$ ${x = -1}$ Now that you know ${x = -1}$ , plug it back into $\thinspace {y = -6x-9}\thinspace$ to find $y$ ${y = -6}{(-1)}{ - 9}$ $y = 6 - 9$ $y = -3$ You can also plug ${x = -1}$ into $\thinspace {2x+3y = -11}\thinspace$ and get the same answer for $y$ : ${2}{(-1)}{ + 3y = -11}$ ${y = -3}$